1. Field of the Invention
The present invention prelates to a display-integrated tablet made by integrating a tablet for inputting position coordinates with a display.
2. Description of the Prior Art
For example, FIG. 9 is a block diagram showing the constitution of the existing display-integrated tablet disclosed in the official gazette of Japanese Patent Laid-open No. 255911/1990. In FIG. 9, symbol 1 is a thin-film EL (electroluminescence) matrix panel in which a plurality of row (top) electrodes Y.sub.1, Y.sub.2, . . . , and Y.sub.n serving as first electrodes and a plurality of column (bottom) electrodes x.sub.1, x.sub.2, . . . , and x.sub.n provided under the first electrodes and serving as second electrodes are arranged like a lattice and a panel surface 1a is mounted on the first electrodes. Symbol 2 is a row (top) electrode driver (first-electrode driver), 3 is a column (bottom) electrode driver (second-electrode driver), and 4 is a timing generator. The row (top) electrode driver 2 and the column (bottom) electrode driver 3 are controlled by the timing generator 4.
Symbol 5 is a pen-type position detecting conductor (hereafter referred to as "pen"), 6 is a detection-signal amplifier, 11 is a comparator, 12 is an AND circuit, and 7 is a peak-timing detecting section for detecting the peak timing of the detection level for scanning-pulse capacitance linkage.
Symbol 8 is a row coordinate (y coordinate) detecting section (first-electrode position detecting section), and 9 is a column coordinate (x coordinate) detecting section (second-electrode position detecting section).
And, FIG. 10 shows the drive timing for the panel 1.
The following is the description of the operation. As shown in FIG. 10, a scanning pulse Py is sequentially supplied to the row electrodes Y.sub.1, Y.sub.2, . . . , and Y.sub.n from the row electrode driver 2 in the display data V.sub.SD supplied simultaneously to the column electrodes x.sub.1, x.sub.2, . . . , and x.sub.n from the column-electrode driver 3 for each scanning line. Therefore, display drive according to line sequential scanning is performed and an image corresponding to the display data V.sub.SD is displayed.
In the row-coordinate (y-coordinate) detection mode, the scanning pulse Py' is sequentially supplied to the row electrodes Y.sub.1, Y.sub.2, . . . , and Y.sub.n from the row-electrode driver 2. In this case, while the scanning pulse Py' is simultaneously supplied to a plurality of adjacent electrodes among the row electrodes Y.sub.1, Y.sub.2, . . . , Y.sub.n the adjacent electrodes are sequentially scanned. That is, the width of the scanning pulse Py' is increased and seqnential scanning is performed while the scanning pulse Py' is simultaneously supplied to a plurality of adjacent electrodes (e.g. 20 adjacent electrodes).
In the column-coordinate (x coordinate) detection mode, the scanning pulse Px' is sequentially supplied to the row electrodes x.sub.1, x.sub.2, . . . , and x.sub.n from the column-electrode driver 3. In this case, while the scanning pulse Px' is simultaneously supplied to a plurality of adjacent electrodes among the row electrodes x.sub.1, x.sub.2, . . . , and x.sub.n, the adjacent electrodes are sequentially scanned. That is, the width of the scanning pulse Px' is increased and sequential scanning is performed while the scanning pulse Px' is simultaneously supplied to a plurality of adjacent electrodes (e.g. 20 adjacent electrodes).
And, periods for display mode, row-coordinate detection mode, and column-coordinate detection mode are optionally set in each frame by means of time division.
Moreover, by contacting the pen 5 with any position on the panel 1, one of the scanning pulses Px' and Py' is detected as a detection signal due to capacitance linkage.
The detection signal of the pen 5 is supplied to and amplified by the amplifier 5. The detection signal Vs outputted from the amplifier 6 is supplied to the comparator 11 and compared with the reference voltage Vr. From the comparator 11, the high-level signal "1" is outputted when the detection signal Vs is higher than the reference voltage Vr and the low-level signal "0" is outputted when the former is lower than the latter. The output signal of the comparator 11 is supplied to the AND circuit 12.
The detection signal Vs outputted from the amplifier 6 is supplied to the peak-timing detecting section 7. From the peak-timing detecting section 7, the detection signal Vs is outputted, that is, the high-level signal "1" is outputted at the peak timing of the detection level for capacitance linkage of the scanning pulse and the low-level signal "0" is outputted except for the peak timing. The output signal of the peak-timing detecting section 7 is supplied to the AND circuit 12.
From the AND circuit 12, the high-level signal "1" is outputted only when the detection signal Vs is higher than the reference signal Vr and the peak timing of the detection signal is detected and the low-level signal "0" is outputted except for the above case. The output signal of the AND circuit 12 is supplied to the row-coordinate detecting section 8 and the column-coordinate detecting section 9.
In this case, the row-coordinate detecting section 8 comprises a counter, to which a reset signal is supplied from the timing generator 4 and reset before the row-coordinate detection mode is set. At the same time, clocks are supplied and counted at the timing when the scanning pulse Py is sequentially supplied to the row electrodes Y.sub.1, Y.sub.2, . . . , and Y.sub.n of the panel 1 and counting is stopped at the timing when the output signal of the AND circuit 12 is set to "1". Therefore, a counted value corresponding to any position on the panel 1 with which the pen 5 contacts is obtained from the row-coordinate detecting section 5 as a row-coordinate output.
Also for the column-coordinate detecting section 9, a counted value corresponding to any position on the panel 1 with which the pen 5 contacts is obtained as a column-coordinate outpost.
Because the existing display-integrated tablet is constituted as described above, it is necessary to supply a scanning pulse to the row and column electrodes of the matrix panel or the first and second electrodes of the matrix panel 1 in the detection mode. Especially, because the detection signal level is greatly decreased due to the capacitance linkage between the second electrodes and pen-type position detecting conductor and thereby, the detection level is raised, there is a problem that the scanning pulse must be supplied simultaneously to, for example, 20 adjacent electrodes and the power consumption increases.
The present invention is made to solve the above problem and its object is to provide a display-integrated tablet realizing position detection only with the first electrodes of a matrix panel without using the second electrodes of it with which position detection is difficult in the detection mode and consuming less power.
Another object of the present invention is to provide a display-integrated tablet easily detecting electrode positions even if the scanning pulse for position detection is greatly attenuated in using a large-screen matrix panel.